Such intramedullary nail systems are known in the field of osteosynthesis which serves the fixation of fragments of a broken or diseased bone in its uninjured, natural form stable to loading by implanted screws, supporting plates, wires, intramedullary nails and the like which are generally made of stainless steel or titanium alloys. These osteosynthesis means permit speedy mobilization of the patient whilst resting the injured bone as is vital for its healing.
Problematic with a rigid fixation by comparatively unelastic, tissue-displacing supporting implants is, however, the hinderance to biological recuperation particularly due to the loss of blood vessels and nerves. Apart from this, the longer the implantation duration the more the biomechanical quality of the supporting structure suffers due to the partial withdrawal of its function. Loss of biological inspection increases, however, the risk of infection by resistant bacteria (MRSA=multiresistant staphylococcus Aureus) which, it has been shown, can colonize the surface of metal implants in the form of an adherent biofilm and withstand antibiotics by a mucuous sheath of polysaccharides.
These problems can be relieved in the scope of orthopedic surgery by magnetically induced electrical osteotherapy, for instance, in making use of the intramedullary nail systems as cited at the outset as described for example in DE 26 36 818 C2. In electrical osteotherapy low-frequency electrical AC potentials are induced in means of osteosynthesis by exposing the afflicted body part to a magnetic alternating field. Numerous clinical applications of this technique in the treatment of bone defects, cysts and tumor metastases chronically resistant to therapy and usually involving an infection as well as near-clinical experimental studies have long since shown that an optimum healing effect is achieved by using osteosynthesis implants as sources of extremely low-frequency sinusoidal AC potentials in the region of the bone adjoining the supportive metal.
The principle involved in transmission is the same as that of a transformer: the injured or diseased region of the body is flooded with a sinusoidal magnetic field of extremely low frequency in the range of approx. 1 to 100 Hz—preferably 4 to 20 Hz—and a magnetic flux density in the range of 0.5 to 5 mT (5 to 50 Gauβ) generated by a function current generator in one or more—primary—outer current coils into which the part of the body provided with the osteosynthesis means is inserted. These electromagnetic fields of extremely low frequency pass through the tissue practically with no loss, including any clothing and a plastercast, as well as the non-magnetic (austenitic) supporting metals of the osteosynthesis. In electrical contact therewith a—secondary—coil assembly, the so-called transmitter, is implanted. The electrical potentials induced in the transmitter are thus brought into effect in the region of the bone lesion as well as generally in the tissue bordering the means of osteosynthesis.
This technique of inductive transmission of therapeutically effective electrical potentials to the components of the osteosynthesis avoids the risk of infection by percutane electrical conductors and the treatment parameters voltage, frequency, intensity, signal shape and treatment time with indication-specific programming of a function current generator of the induced magnetic field can be determined.